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JAKE TAPPER, CNN ANCHOR: ISIS terrorism shipped straight from Syria.

THE LEAD starts right now.

Sources now telling CNN that the suicide bombers who unleashed hell in Istanbul, killing 44 innocents and maiming hundreds more, were foreign fighters on a terrorist mission from ISIS leaders exported directly from ISIS headquarters.

Then, voting themselves into oblivion? Mitt Romney suggests that Republicans who vote for Donald Trump might be helping American commit suicide. And now other Republican leaders are denouncing Trump as an ignoramus and a 6-year-old.

And a time when Hillary Clinton is trying to push back on the notion that she is untrustworthy and that she and her husband think the rules don't apply to them, her husband has a friendly conversation with the attorney general, just a friendly chat between the man married to the presumptive Democratic presidential nominee and the chief law enforcement officer, who is ultimately responsible for the FBI probe of her private e-mail server.

Good afternoon, everyone. Welcome to THE LEAD. I'm Jake Tapper.

Some new hair-raising details about the slaughter at Istanbul's Ataturk Airport that killed 44 innocent people earlier this week. Turkish officials telling CNN that not only was ISIS definitively behind the terrorist attack, but also that Islamic terror group's leaders carefully planned, crafted, and even directed the massacre.

This as we're getting a glimpse of the devastation in Istanbul just moments after one of the suicide bombers blew himself up inside the airport. Also, new surveillance video obtained by Turkish media outlet HaberTurk captures the moment one of the ISIS terrorists tried to assassinate an undercover police officer.

According to Turkish sources, the three suicide bombers were foreign fighters from former Soviet Bloc countries. That had travelled all the way from Central Asia and Eastern Europe to Raqqa, Syria, which is the headquarters for ISIS, before being dispatched to Turkey.

Sources also say evidence indicates the terrorists entered Turkey with the suicide vests and bombs used in the attack.

Let's bring in CNN senior international correspondent Nima Elbagir live in Istanbul, Turkey.

Nima, Turkish officials conducted overnight raids across Turkey. Did they glean any new information from those raids about how this terrorist attack may have been carried out?

NIMA ELBAGIR, CNN CORRESPONDENT: Well, much of what was this collaboration between both the homegrown terror network here who have links to ISIS and were responsible for two of the recent terror (INAUDIBLE) over the last few months and directly working alongside, directly working under the oversight of the ISIS leadership in Raqqa.

Take a look at this, Jake.

(BEGIN VIDEOTAPE)

ELBAGIR (voice-over): One terrorist is seen wearing a heavy coat despite the summer heat in Istanbul. When an undercover cop asks for identification, he is shot. Another surveillance camera catches a terrorist tearing through the airport armed with a rifle. A Turkish government official tells CNN the men in these videos are believed to have been directed by ISIS leadership in Syria.

UNIDENTIFIED MALE (through translator): These people are not Muslim. They're going to be the occupants of hell. They have secured their places in hell.

ELBAGIR: Today, Turkish police conducted raids across the country in connection to the attack, rounding up more than 20 people.

UNIDENTIFIED MALE (through translator): The evidence, documents, and findings we have obtained corroborate the predictions that this attack was carried out by ISIS.

ELBAGIR: Still, there has been no claim of responsibility, and while the government here is convinced ISIS was behind the attack, which has not left more than 40 people dead and hundreds more injured, it hasn't said it believes others were directly involved.

What Turkish authorities will say is that they believe the three men were foreign fighters, originally from Russia, Uzbekistan, and Kazakstan. Sources tell CNN they arrived here last month carrying their suicide vests after receiving training from ISIS in Raqqa, Syria.

CNN has learn they rented an apartment where the Russian man apparently left his passport. Today, the U.S. homeland security secretary echoed the Turkish government, saying that attack has all the hallmarks of ISIS. He confirmed one American was injured Tuesday, although he described the injuries as minor.

(END VIDEOTAPE)

ELBAGIR: Jake, neighbors in that very apartment building told us just a few hours ago that they had been concerned for days about the smell of chemicals that was permeating the entire building, emanating from the attackers' apartment.

TAPPER: All right, Nima Elbagir in Istanbul, Turkey, thank you so much.

Joining me right now, Republican Senator Richard Burr of North Carolina. He is the chair of the Intelligence Committee in the Senate.

Mr. Chairman, thanks so much for being here. You just got out of a briefing. what's the latest you can tell us about the investigation?

SEN. RICHARD BURR (R), NORTH CAROLINA: Well, Jake, as you know, we have had quite a few of these lately.

And it takes time for the forensics, especially when it's overseas. But I think it's safe to say that it has all the hallmarks of an ISIL- directed attack, that because of the degree of planning and the tactical coordination, this is something that was looked at for probably quite some time.

[16:05:18]

It was an airport that we knew was surveilled in the past. For reason, we didn't know. But obviously that surveillance took effect with this attack this week.

TAPPER: Were any of the terrorists or any of the ISIS individuals who may have been involved in one way or another known to Turkish officials, European officials, or American officials?

BURR: Too early to know. I don't want to speak for the Turks. They're the lead investigator. And it takes awhile before their information feeds to us. And the faster that they share information with us, the faster we would be able to make direct links around the world, because we have the largest database for that.

But I would not read too much into it until we know exactly who they were. I know there is speculation now. But they have got very little evidence right now to go on unless they have found additional evidence.

TAPPER: Well, they seem to have the nationalities of the three terrorists at least. They're talking about them being from specific countries, including Russia. That would suggest that they have an idea of who they are, no?

BURR: It would suggest that they had confirmed by either people that lived near them or individuals that they have picked up. I think they have picked up 13 individuals in raids that they have committed.

But as you and I have seen before, in an event like this, for weeks, there will be additional raids on individuals. I think the question is, what will this do to Turkey's commitment to close the border? Will Turkey start being a real participant in prosecuting the war against ISIS? And will the United States adjust its strategy to make sure that these types of attacks can't continue to happen throughout Europe and potentially here in the U.S.?

TAPPER: What you and other national security officials have been saying is that this has all the hallmarks of an ISIS- or ISIL-directed attack. But is there specifically any intelligence, any information showing communication with these individuals, or is it just the fact that they have identified who they are, and they have traced them to Raqqa and then traced them back to Eastern Europe? Is that -- is it just their path more than anything else?

BURR: No electronic media that has been looked at that would give that direct link today.

But that is not to say that, as the forensics is done on that, that we might not find a communication that shows a direct communication with individuals in Raqqa, or, I might say, in 19 other countries where al Qaeda has a presence and six of them with operational capacity.

TAPPER: Al Qaeda and ISIS.

BURR: And ISIS. Excuse me.

TAPPER: And let me ask you a question, because it seems like ISIS is being defeated quite a bit on the battlefield, at least in some areas, including Iraq.

They just lost Fallujah the other day. Some speculate that every time they lose territory in their so-called caliphate, in the land that they have taken control of, they strike out in other places in Europe or Turkey or wherever. Is that accurate? And is it directly correlated? Or is it just that they are always attacking and the war is going on in the Middle East?

BURR: Well, two answers.

One is they have given up 20 percent of the geography. And they have lost quite a few fighters. Their net has spread to 19 countries. And that means that we have got to follow them with our coalition partners.

I think, more importantly, I said for the last year when I have had the opportunity to come on with you, with every day, the threat scenario gets worse. And it is worse today than it was when this attack happened, from a standpoint of how many places around the world that there is a commitment to carry out a terrorist act.

And what we have got is an intent and capabilities. And when we don't affect one of those two, it is a matter of time before the next one and the next one and the next one.

TAPPER: And let's talk about that, because I know a lot of people are watching at home. It's the Fourth of July holiday coming up.

How safe is and secure is the United States from this threat? Is there any actionable intelligence about any terrorism that might be committed in the next week or so?

BURR: No actionable intelligence, but the intent and the capability exists, whether that is through directed, enabled, or just a individual that is homegrown and radicalized, that something could happen in the United States.

So, when you see something say something is a really, really important phrase. In Turkey, we now have individuals that say I smelled chemicals in the building. Didn't say anything.

So, we learn with each one, but, as you pointed out, as the war begins to affect ISIL's presence in the caliphate, the likelihood is, these will become more frequent around the world, and the United States is not excluded from that just because we have two oceans as borders.

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TAPPER: Senator Burr, thanks so much. As always, we appreciate your time. Have a happy Fourth of July in that beautiful state of yours, North Carolina. Appreciate it.

BURR: You too. Thank you, Jake.

TAPPER: ISIS taking a direct hit on the battlefield. A major coalition strike destroys two massive ISIS convoys. What might this mean for a key battle coming up ahead? That story next.

(COMMERCIAL BREAK)

TAPPER: Welcome back to THE LEAD.

Some tragic breaking news right now. Today, the State Department confirmed that a teenaged girl in a terrorist attack in the West Bank this morning was a U.S. citizen.

Her mother says her 13-year-old daughter was attacked in her bed while she was asleep. The girl's name, Hallel Yaffe Ariel. The Israeli military says a 17-year-old Palestinian stabbed her to death in her sleep. Security guards arrived at the home and killed him after the attack.

This makes at least seven U.S. citizens killed by terrorist attacks in Israel and the West Bank in just the last year.

Turning now to the U.S.-led war on ISIS in Iraq and Syria, according to the Pentagon, as many as 300 ISIS militants have been killed after joint airstrikes destroyed two massive convoys of trucks fleeing their former stronghold of Fallujah, which Iraqi troops recaptured this week with the help of the United States.

the secretary of defense really putting his cards on the table there, just as these massive air strikes in Iraq put ISIS under additional pressure. This is a battlefield that is now changing almost every day.

(BEGIN VIDEOTAPE)

STARR (voice-over): ISIS fighters under cover of darkness trying to outrun U.S. and Iraqi war planes. South of Falluja, hundreds of ISIS operatives and 200 vehicles or more busted through a cordon trying to escape the Iraqi government liberation of the city. War planes swooped in, the U.S. destroyed up to 50 vehicles. Iraqi forces bombing dozens more.

One military estimate, more than 300 ISIS dead. The stakes are accelerating at the Pentagon with eyes quickly turning towards the ISIS capital city.

ASH CARTER, SECRETARY OF DEFENSE: We'd like to get Raqqa as soon as we possibly can.

STARR: Defense Secretary Ash Carter bluntly signaling the next move to ISIS leaders by U.S. aircraft and anti-ISIS fighters in northern Syria.

CARTER: We are going to position to again envelop and collapse ISIS control of Raqqa. And reason I want to do that, Barbara, as soon as possible, is that Raqqa is the self-proclaimed capital of the self- proclaimed caliphate of ISIL.

STARR: Getting to Raqqa is increasingly urgent. The attackers in Istanbul airport assault travelled from Raqqa according to Turkish officials and the CIA director is warning more may be headed to Europe.

JOHN BRENNAN, CIA DIRECTOR: ISIL is training and attempting to deploy operatives for further attacks. ISIL has a large group of fighters that could serve as operatives for attacks in the West.

STARR: It comes as Washington is discussing with Moscow whether their two militaries can cooperate more in Syria, a more urgent concern with Raqqa now firmly in the crosshairs.

UNIDENTIFIED MALE: The U.S. have been putting U.S. ground troops, advisers, to assist U.S.-backed rebels on the ground. That's certainly something we'll have to be able to do as is to communicate to the Russians, here is where our people are so that Russians aren't bombing our own troops on the ground.

(END VIDEOTAPE)

STARR: Now, why would Ash Carter signal ISIS about what the next moves are? Well, look at what happened in that open desert? When ISIS is under pressure, they start to move around and that makes it so much easier for ISIS strikes to find them -- Jake. TAPPER: Barbara Starr at the Pentagon for us -- thank you so much.

Hillary Clinton and the Democrats are not the only ones that Donald Trump thinks he is running against. Who else does the presumptive Republican presidential nominee say he is trying to beat?

Plus, hundreds of thousands of driverless cars are told stop using their cars immediately. What sparked that strong warning?

(COMMERCIAL BREAK)

[16:22:28] TAPPER: Welcome back to THE LEAD.

You're looking at some live pictures from Donald Trump, the presumptive Republican presidential nominee, taking questions from voters in New Hampshire.

Welcome back to the show.

The presumptive Republican nominee has had his ups and downs with the Republican Party establishment. But many in his party hope to put all that discord behind them before the party's convention next month. Well, maybe not.

CNN senior White House correspondent Jim Acosta is covering Trump in Manchester, New Hampshire, right now.

Jim, one of the ways he has worked to appease party establishment is by talking about policy. Right now, you hear him talking about trade, but it should be pointed out that his views on trade are drawing comparison to the views of Senator Bernie Sanders. And that comparison is coming from Trump himself.

JIM ACOSTA, CNN SENIOR WHITE HOUSE CORRESPONDENT: That's right, Jake. Donald Trump is veering off of the typical GOP playbook. You can say he's holding a town hall in Manchester, New Hampshire, right now. He is taking questions from voters here.

But that's right. Just a few moments ago, he was offering some very tough talk on trade. He joked at one point, when a plane was flying over head, that perhaps that plane was from Mexico preparing to attack.

You know, Jake, he has been really working off of the script, off the teleprompters in recent days, even suggesting lately that those in his party who won't really behind his campaign are a disgrace.

(BEGIN VIDEOTAPE)

ACOSTA (voice-over): Just weeks before he's set to become the Republican nominee, Donald Trump isn't feeling like the life of the party.

TRUMP: It's almost, in some ways, like I'm running against two parties. But I'm not sure it matters because I think we're going to win. ACOSTA: Trump is now openly complaining at his rallies about his past

rivals who are refusing to endorse him despite signing a GOP loyal pledge to support the party's eventual nomine. The document Trump agreed to himself.

TRUMP: They broke their word. In my opinion, they should never be allowed to run for public office again because what they did is disgraceful.

ACOSTA: But it's not just Trump's opponents from the primaries. GOP senators are hesitating to get board, big time.

SEN. SUSAN COLLINS (R), MAINE: Donald Trump was not my second choice, he was not my third choice. And I'm going to see what happens at the convention. It's going to be very important to me whom Donald Trump chooses as his running mate. And that is arguably the most important decision that a candidate can make.

ACOSTA: On Trump's vice presidential campaign search, CNN has learned New Jersey Governor Chris Christie is being vetted by the campaign. But one cautions it's not clear how high Christie is on the list.

[16:25:01] Utah Senator Like Lee in an interview with "The Huffington Post" is urging Trump to consider Texas Senator Ted Cruz, but Lee is still furious that Trump once floated a bogus conspiracy theory about Cruz's father.

SEN. MIKE LEE (R), UTAH: We can get into the fact that he accused my best friend's father of conspiring to kill JFK.

ACOSTA: Lee says he is not ready to back Trump either.

LEE: I'd like some assurances that he is going to be a vigorous defender of the U.S. Constitution. That he's not somebody who's going to abuse a document to which I've sworn an oath to uphold and protect and defend.

ACOSTA: And Trump's attacks on key GOP friendly groups like the U.S. Chamber of Commerce are making Republican insiders even more nervous.

TRUMP: The U.S. Chamber of Commerce is totally controlled by the special interest groups.

ACOSTA: Which brings a lot of Republicans back to their last nominee, Mitt Romney.

MITT ROMNEY (R), 2012 PRESIDENTIAL NOMINEE: My wife and kids wanted me to run again this time interestingly enough. And I got an e-mail from my sons yesterday saying, you've got to get in, dad, you've got to get in.

ACOSTA: But Romney added, don't hold your breath.

ROMNEY: But the idea of running and asking people to come around me with a sole purpose of being a spoiler is not something I can go out in good faith to donors and the workers and voters and say, come help me stop this candidate or that candidate.

ACOSTA: Romney also offered this warning from one of the Founding Fathers, John Adams.

ROMNEY: Every democracy commits suicide.

(END VIDEOTAPE)

ACOSTA: Now, there's a recent poll that shows, Jake, that more than half of Republicans would rather see somebody else be their nominee than Donald Trump. But, of course, Donald Trump feels points to polls where he feels like he is doing well.

And when it comes to this talk on trade, they do acknowledge inside the Trump campaign that there are going to be some Republicans who don't like what he has to say. But they feel like this kind of rhetoric, this kind of message also pulls in perhaps some Bernie Sanders supporters and disaffected Democrats in places like New Hampshire and Pennsylvania that may balance that out -- Jake.

TAPPER: All right. Jim Acosta, traveling with the Trump campaign in New Hampshire, thanks so much.

She is the nation's top law enforcement officer, overseeing the investigation into Hillary Clinton's private e-mail server. Now, even Democrats are asking questions about why Attorney General Loretta Lynch meet privately with former President Bill Clinton on a tarmac in Arizona?